Polishing pad for CMP, method for polishing substrate using it and method for producing polishing pad for CMP

ABSTRACT

In CMP technology for planarizing an interlayer insulation film, a BPSG film, an insulation film for shallow trench isolation, or the like, in the production process of a semiconductor element, irregularities of a matter being polished, e.g. a silicon oxide film, are planarized efficiently at a high speed while suppressing the occurrence of polishing flaws on the substrate by employing a polishing pad having organic fibers exposed on the surface thereof abutting against the matter being polished.

TECHNICAL FIELD

The present invention relates to a polishing pad for CMP, which isusable in the chemical mechanical polishing (CMP) method employed in theproduction technology of semiconductor elements and in the polishingmethod employed in thee production technology of hard discs. The presentinvention further relates to a method for polishing a substrate by usingthe polishing pad and to a method for producing a polishing pad.

BACKGROUND ART

In the present ultra large scale integrated circuits, packaging densityis increasing, and a variety of fine processing techniques are beingstudied and developed. Design rule has already been of the order ofsub-half-micron. One of the techniques developed to meet the requirementfor such a strict miniaturization is the CMP (chemical mechanicalpolishing) technique. In the production process of semiconductordevices, this technique can completely planarize a layer to be exposedto light, thereby lightening the burden of exposure techniques andstabilizing the yield. This, therefore, is a technique essential forplanarizing an interlayer insulation film or a BPSG film, shallow trenchisolation, etc.

According to the conventional polishing method employed in theproduction process of semiconductor devices to planarize an inorganicinsulation film, such as a silicon oxide insulation film formed byplasma-CVD (Chemical Vapor Deposition), low-pressure-CVD, etc., asubstrate on which a film to be polished is formed is pressed against apolishing pad, and the substrate or the polishing pad is moved whilefeeding an abrasive between the film to be polished and the polishingpad.

A polishing pad made of polyurethane foam has commonly been used in theabove-described method, which however is insufficient in the speed ofpolishing the inorganic insulation film, and involves the great problemthat polishing flaws occur during polishing on the surface of the oxidefilm due to polishing particles. In the case of a pad made of a foamedor non-foamed resin, decreasing the hardness of the pad surface reducesthe polishing flaws effectively, but materials of low hardness do notsuit to planarize irregularities efficiently in the production ofsemiconductor devices. To solve the problem, pad materials compromisingthe reduction of polishing flaws and the improvement of flatness areused, but are not enough to solve the problem of polishing flaws.

DISCLOSURE OF INVENTION

The present invention provides a polishing pad and a method of polishinga substrate whereby in the CMP technology employed in the production ofsemiconductor elements for planarizing an interlayer insulation film, aBPSG film, an insulation film for shallow trench isolation, etc.,irregularities on a matter to be polished, such as a silicon oxide film,are planarized efficiently at a high speed while suppressing theoccurrence of polishing flaws on the substrate. The present inventionfurther provides a method of producing the polishing pad.

The present invention has been made on basis of the finding that in theCMP technology for planarizing a interlayer insulation film, a BPSG filmor an insulation film for shallow trench isolation, a silicon oxide filmis polished at a high speed while suppressing the occurrence ofpolishing flaws by using a polishing pad for CMP having a very thinfiber layer on the surface of an elastic body.

Accordingly, the present invention relates to a polishing pad forpolishing a substrate or a thin film formed on a substrate, whichpolishing pad contains organic fibers exposed on a surface of thepolishing pad.

The present invention further relates to a polishing pad having amultilayer structure, comprising the above-described polishing pad and alayer, which are laminated together and have different elastic moduli.

The present invention further relates to a polishing pad material thatmay be suitably used for the production of the polishing pad. Thepolishing pad material has a plate-like shape, comprises fibers and aresin fixing the fibers to form the plate-like shape, and has at leastone surface layer which is substantially non-porous and comprisesorganic fibers and the resin fixing the organic fibers.

The present invention also relates to an advantageous method ofproducing the above-described polishing pad.

Accordingly, the present invention relates to a method of producing apolishing pad by using a polishing pad material of a plate-like shape,which comprises fibers and a resin fixing the fibers to form theplate-like shape and has at least one surface layer being substantiallynon-porous and comprising organic fibers and the resin fixing theorganic fibers. According to this method, the surface of the surfacelayer of the polishing pad material is mechanically polished, so thatthe surface layer has a surface on which the organic fibers are exposed(first production method).

The present invention further relates to a method of producing apolishing pad, comprising layering a resin-impregnated sheet-form fiberbase material and a resin-unimpregnated sheet-form fiber base materialso that a resin-unimpregnated sheet-form fiber base material comprisingorganic fibers is located on at least one surface, and unifying them bythermocompression molding to form a polishing pad having at least onesurface on which the organic fibers are exposed (second productionmethod).

The present invention further relates to a method of producing apolishing pad, comprising layering a resin-impregnated sheet-form fiberbase material and a resin-unimpregnated sheet-form fiber base materialso that a resin-unimpregnated sheet-form fiber base material comprisingorganic fibers is located on at least one surface, unifying them bythermocompression molding to form a polishing pad material having nosurface on which the organic fibers are exposed, and allowing theorganic fibers to be exposed by mechanically polishing the surface ofthe polishing pad material on which the resin-unimpregnated sheet-formfiber material is located (third production method).

The present invention further relates to a method of polishing asubstrate, comprising pressing the substrate against the surface of thepolishing pad of this invention on which the organic fibers are exposed,and relatively sliding the substrate and the polishing pad while anabrasive is being fed between the substrate and the polishing pad.

Polishing a semiconductor substrate by using the polishing pad of thepresent invention having a surface on which an exposed fiber layer oforganic fibers is formed enables planarization at a high speed andreduction of polishing flaws. The reason is presumed as follows. Thereason for the high polishing speed may be that polishing particles areefficiently held between and on the surfaces of the exposed fibers andcontact the surface being polished with increased frequency. The reasonfor the reduction of the occurrence of flaws on the matter beingpolished may be as follows. Among foreign matters and polishingparticles, huge ones have possibly caused the occurrence of flaws, butwhen they are sandwiched between the surface of a matter being polishedand the exposed organic fiber layer, they dig themselves into the bundleof fibers and escape from high-pressure contact with the matter beingpolished.

Being molded with a resin-unimpregnated sheet-form fiber base materialcomprising organic fibers, the polishing pad produced by the secondproduction contains in its surface part some resin oozing out from thelower layers on molding, but the resin content in the surface part is sosmall as to provide a good layer of exposed organic fibers on thesurface. The resin oozing out in the surface part fixes the basal partsof the organic fibers securely and keeps the layer of exposed organicfibers for a long term.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a polishing pad of an embodiment accordingto the present invention.

EXPLANATION OF SYMBOLS

1: elastic body layer

2: exposed fibrous layer

BEST MODE FOR CARRYING OUT THE INVENTION

Herein, the state where organic fibers are exposed on a surface of apolishing pad means that organic fibers are protruding from and exposedon at least one surface of an underlying layer, such as an elastic body.

A pad of an embodiment according to the present invention having a verythin exposed fibrous layer on a surface of an elastic body will bedescribed referring to FIG. 1. FIG. 1 illustrates a sectional view ofthe polishing pad. Organic fibers are exposed on an elastic body layer 1made of a resin or an FRP (fiber reinforced plastic) and form a verythin exposed fibrous layer 2.

The structure of the polishing pad of the present invention is notparticularly limited, and may be any one, which has, at least on use,organic fibers exposed on the surface abutting to a matter beingpolished. A preferred example of the structure comprises a resincontaining organic fibers. The organic fibers exposed on the surfacepreferably have a length of 1 cm or less, more preferably 3 mm or less.For example, the exposed parts of the organic fibers preferably have afiber length of 10 μm to 1 cm, more preferably 10 μm to 3 mm, furtherpreferably 50 to 500 μm. The organic fibers exposed on the surfacepreferably have a fiber diameter of 1 mm or less, for example,preferably 1 μm to 1 mm, more preferably 10 to 50 μm. The wholepolishing pad preferably has a thickness of 0.1 to 5 mm, more preferably0.5 to 2 mm.

As to the degree of exposure of the organic fibers on the surface of thepolishing pad, it is preferable that on average at least one organicfiber having the above-described length is exposed in every squaremillimeter of the pad surface, and the more, the better. Some organicfibers longer than the above-described preferable exposed length may beincluded, for example, one or less fiber per square centimeter onaverage. The diameter of the organic fibers exposed on the surfacedepends on the diameter of the starting organic fibers as describedlater, but strands of twisted organic fibers may be unbound and exposedas thinner fibers.

Examples of the organic fibers include fibers of an aramid, a polyesteror a polyimide. In case where the polishing pad is made of a resincontaining organic fibers, chops obtained by cutting monofilaments oforganic fibers into a predetermined length or pulps obtained by smashingchops may be contained in the underlying layer separately, or organicfibers may be contained in the resin in a form of woven fabric orunwoven fabric. Provided that the organic fibers need protrude from theunderlying layer and be exposed on at least one surface of the polishingpad. Organic fibers of a non-woven fabric form are firmly fixed by theresin, and their exposed parts have a well nappy form on the surface ofthe polishing pad. They have another advantage that no texture appearson the surface of the polishing pad.

Preferred organic fibers are aramid fibers, which may be used alone oras a chief fibers. The reason is that aramid fibers have higher shearstrength than the common organic fibers, and can be exposed in a betterstate by mechanically polishing the surface of the polishing pad. Inaddition, their high tensile strength improves the durability of thepolishing pad, extending its lifetime. Aramid fibers include para- andmeta-aramid fibers, and para-aramid fibers are preferable to extend thelifetime of the polishing pad by suppressing wear because they havebetter mechanical properties (e.g. tensile strength) than meta-aramidfibers. Para-aramid fibers are suitable for the moist polishingenvironment because they are less hygroscopic than meta-aramid fibers.As para-aramid fibers, poly-p-phenylene terephthalamide fibers andpoly-p-pheneylenediphenylether terephthalamide fibers are commerciallyavailable and may be used in the present invention.

The underlying layer under the exposed fibrous layer (the layer oforganic fibers exposed on a surface) is preferably an elastic bodylayer, such as a resin substrate having a high elastic modulus, whichincreases the efficiency of planarizing irregularities compared with apad made of only a resin having a low elastic modulus or a pad producedby allowing organic fibers to adhere to the surface of a resin substratehaving a low elastic modulus. In case where the elastic body layer as aunderlying layer is made of an FRP that is a resin containing the sameorganic fibers as that exposed on the surface, the exposed fibersdisappeared by abrasion due to polishing or by dressing with a diamondwhetstone attached to a polishing apparatus, but are regenerated by thenew exposure of the fibers contained in the resin in the underlyinglayer, and the exposed fibrous layer on the surface is maintained.Accordingly, the polishing pad for CMP reconciles reduction of polishingflaws and improvement of flatness, and is durable and stable enough forgood productivity. Examples of resins having low elastic modulus includepolyurethane and polyethylene, and examples of resins having highelastic modulus include epoxy resins, acrylic resins and polystyrene.

The underlying layer may have a multilayer structure produced bylaminating resin or FRP layers having different elastic moduli. Forexample, the distribution of the polishing speed in the surface of asubstrate being polished can be stabilized by forming an exposed fibrouslayer on a surface of a layer having a high elastic modulus andproviding a layer having a low elastic modulus under the layer.

As to the materials usable in the polishing pad of the presentinvention, examples of the organic fibers to be exposed on a surfaceinclude above-mentioned aramid fibers, polyester fibers and polyimidefibers, and the resin may be any one that can be formed into a plateshape, such as an epoxy resin. According to a preferred productionmethod of the polishing pad of the present invention, prepregs arepreviously prepared by combining fibers and a thermosetting resin.Desired numbers of the prepregs are then molded into a plate shape bythermocompression molding (thermal pressing curing), and organic fibersare exposed on a surface at the same time of the molding or bymechanical polishing, such as dressing after the molding. The fiberdiameter of the organic fibers used as a material may be 1 mm or less,preferably 50 μm or less, more preferably 1 μm to 1 mm, furtherpreferably 10 to 50 μm. Inorganic fibers, such as glass fibers, may alsobe used for the production of the prepregs except for the prepreg to belocated on a surface for exposing organic fibers on a surface of thepolishing pad. The inorganic fibers may be chops obtained by cuttingmonofilaments into a predetermined length or pulps obtained by smashingchops, or may be woven fabric or non-woven fabric. Preferred examples ofthermosetting resins include epoxy resins, such as bisphenol A epoxyresins, phenolic resins and polyimide resins, with epoxy resinsparticularly preferred.

The polishing pad of the present invention may be produced by using apolishing pad material that comprises a resin containing organic fibersand is produced by thermocompression molding as described above, andforming an exposed fibrous layer by mechanically polishing the surfaceof the polishing pad material to expose the organic fibers.

For example, the polishing pad material used in the first productionmethod of the present invention has a plate-like shape and comprisesfibers and a resin fixing the fibers to form the plate-like shape, andhas at least one surface layer which is substantially non-porous andcomprises organic fibers and the resin fixing the organic fibers. Notonly the surface layer, the whole polishing pad material may containorganic fibers fixed by a resin and be substantially non-porous. In casewhere the surface layer (or whole the polishing pad material) contains acombination of two or more kinds or organic fibers being different in atleast one of material, shape, fiber diameter and fiber length, specificeffects can be obtained by selecting the combination. A combination ofrelatively thicker fibers (about 1.5 deniers, e.g. 8-16 μm in fiberdiameter) and relatively thinner fibers (about 0.1 denier, e.g. 0.5-1.5μm in fiber diameter) both of which are made of the same material iseffective to make sure of high polishing speed and flatness because ofthe interaction of the both fibers. The former fibers contribute to theincrease of polishing speed, and the latter to the insurance offlatness. An example is a combination of chops and pulps of para-aramidfibers. A combination of relatively longer fibers (length: about 5 mm,e.g. 3-8 mm) and relatively shorter fibers (length: about 1 mm, e.g.0.5-2 mm) is also preferable. Non-woven fabrics made from mixtures ofdifferent organic fibers can realize such combinations of differentfibers. Varying the kinds of fibers in the direction of the thickness ofthe polishing pad material makes specific effects depending on thecombination of the fibers. In case where a polishing pad materialcomprising a surface layer containing fibers having a high elasticmodulus (e.g. aramid fibers) and an underlying backing layer containingfibers having a low elastic modulus (e.g. polyester fibers) is used andmechanically polished to expose the fibers having a high elastic modulusfrom the surface layer, the surface layer having a high modulus ishardly deformed when a high stress is applied during polishing, and thebacking layer having a low elastic modulus absorbs the stress, so thatevery area of the polishing surface is polished at a uniform speed.Various resins may be used for fixing organic fibers, and some examplesinclude thermoplastic resins, such as acrylic resins and ABS resins, andthermosetting resins, such as phenolic resins, epoxy resins andpolyimides. Thermosetting resins have higher elastic moduli comparedwith thermoplastic resins, and are preferable because they are less wornon polishing or dressing and excel in durability. Epoxy resins havinghigh adhesiveness are particularly preferable. The content of organicfibers in the surface layer is preferably 50% by weight or more, morepreferably 70 to 90% by weight. When polished to form an exposed fibrouslayer, such a surface layer allows much organic fibers to be exposed onthe resulting polishing pad, increasing the effects of reducing theoccurrence of polishing flaws.

In the first production method of the present invention, as describedabove, the organic fibers to be used in the surface layer of thepolishing pad material preferably has a form of a non-woven fabric. Apolishing pad material wherein organic fiber base materials each havinga sheet-form, such as organic fiber non-woven fabrics, may be producedby thermocompression molding a layer of prepreg produced by impregnatingan organic fiber base material with a resin and drying. The molding maybe carried out in the same manner as in the molding of a laminate forelectric insulation. For example, a layer of prepreg produced byimpregnating an organic fiber base material with a thermosetting resinand drying is covered with a release film, sandwiched betweenmirror-finished metallic plates, and thermocompression molded between apressing heating plates. The layer of prepreg may consist of one sheetof prepreg or a plurality of sheets of prepreg. The number of the sheetsof prepreg may be varied, and prepreg of other fiber materials may beused in combination, depending on the kinds of matters to be polished,such as silicon wafer, or on the polishing conditions. An example ofsuch combinations is a polishing pad wherein the surface layer is madefrom aramid fiber base material prepreg, and the backing layer is madefrom polyester fiber material prepreg.

To form an exposed fibrous layer by mechanically polishing the surfacelayer of the above-described polishing pad material, the surface of thepolishing pad material may be previously napped by previously polishingwith a ceramic roll or a sand blast. Alternatively, after the polishingpad material is attached to an apparatus for polishing a substrate, thesurface of the sheet-like pad material described above may be subjectedto the above-described dressing treatment, whereby the resin on thesurface is ground off with a diamond whetstone and fibers are exposed.The diamond whetstone may be replaced by a wire brush, a metal scraper,a resin brush, or a glass or alumina ceramics plate.

As to the conditions of the dressing treatment, in case where a diamondwhetstone is used, the particle size of the diamond particles adheringto the diamond whetstone is preferably not less than #60 count and notmore than #400 count in particle size as established by JIS-B-4130, morepreferably not less than #100 count and not more than #320 count. Thepressure applied during the dressing treatment depends on the polishingapparatus used and the polishing pad material used, and is generally 1to 20 kPa. The revolution speed for the dressing treatment depends onthe polishing machine used. For example, in case of a Mirra machineproduced by AMAT Co., Ltd. (fixing disc diameter: 50 cm), 10 to 100 rpmis efficient.

The state where organic fibers are exposed on a surface by dressingtreatment may be made before beginning polishing of substrates, orbefore polishing every substrate. Alternatively, a polishing padmaterial may be used for polishing substrates without dressing so thatan exposed fibrous layer is formed by the abrasion of the polishing padsurface progressing simultaneously with polishing of the substrates.

It is also possible to produce the polishing pad of the presentinvention by layering, when molding materials containing organic fibersand a resin are thermocompression molded, the molding materials so thatorganic fibers are exposed on the surface of the polishing pad after thethermocompression molding. This method enables the organic fibers to beexposed on the surface of the polishing pad without mechanicalpolishing, such as dressing treatment. For example, when moldingmaterials, such as a resin or FRP, such as prepreg, are formed into aplate like form by pressing, etc., organic fibers in a state of anon-woven fabric or the like may be pressed against the surface of themolding material to transfer the organic fibers. The second productionmethod of the present invention is a preferred embodiment of thisproduction method.

According to the second production method of the present invention, aresin-impregnated sheet-form fiber base material and aresin-unimpregnated sheet-form fiber base material are layered so that aresin-unimpregnated sheet-form fiber base material is located on atleast one surface, and unifying them by thermocompression molding. Theresin-unimpregnated sheet-form fiber base material located on thesurface shall consist of organic fibers. This makes the state where theorganic fibers are exposed on the surface.

The number of each of the resin-impregnated sheet-form fiber basematerial and the resin-unimpregnated sheet-form fiber base material isnot particularly limited, and may be varied depending on the desiredthickness of the polishing pad. Further, the layering order of thesesheet-form fiber base materials is not particularly limited, provided aresin-unimpregnated sheet-form fiber base material comprising organicfibers is located on one surface. For example, at least one, preferably1 to 3 resin-unimpregnated sheet-form fiber base materials may belayered on layered resin-impregnated sheet-form fiber base materials, ora plurality of resin-impregnated sheet-form fiber base materials and aplurality of resin-unimpregnated sheet-form fiber base materials may belayered alternately.

Under the resin-unimpregnated sheet-form fiber base material comprisingorganic fibers and being located on the surface, resin-impregnated or-unimpregnated sheet-form fiber base materials comprising fibers otherthan organic fibers, such as sheet-form glass fiber base materials, maybe used, but preferably resin-impregnated or resin-unimpregnatedsheet-form fiber base materials that also comprise organic fibers. Inthe later case, the exposed organic fibers disappear by abrasion due topolishing or dressing for roughening the surface, but are regenerated bynew exposure of the organic fibers contained in the resin in theunderlying layer, and the exposed organic fiber layer is maintained.

The resin-unimpregnated sheet-form fiber base material may be formed bythe mutual bonding of fibers due to their fusion, or by bonding fibersmutually with an adhesive. Examples of usable adhesives are adhesivescomprising epoxy resins, such as a water-soluble epoxy resin binder. Incase where an adhesive is used, non-limitative but preferable amount ofthe adhesive used is 3 to 20 parts by weight, more preferably 5 to 15parts by weight relative to 100 parts by weight of fibers. The unitweight of the resin-unimpregnated sheet-form fiber base material ispreferably 36 to 100 g/m², more preferably 55 to 72 g/m².

The resin-impregnated sheet-form fiber base material is produced byimpregnating a resin-unimpregnated sheet-form fiber base material with aresin. The content of the fiber base material in the resin-impregnatedsheet-form fiber base material is preferably 60 to 140 parts by weight,more preferably 90 to 120 parts by weight relative to 100 parts byweight of the total of the resin and adhesive used.

The content of resin-unimpregnated sheet-form fiber base material in thewhole body may be selected considering the content of fibers in apolishing pad, particularly the content of organic fibers in the surfacelayer to be pressed against a matter being polished. According to thismethod, the content of fibers in a polishing pad can be varied byvarying the ratio of resin-unimpregnated sheet-form fiber base materialsused, without varying the impregnating amount of a resin used for theproduction of prepreg.

In the thermocompression molding, heating temperature is generally 150to 200° C., preferably 160 to 180° C., and pressure is generally 50 to500 kPa, preferably 200 to 400 kPa.

According to second production method, the state where organic fibersare exposed on a surface can be made without mechanical polishing, butpolishing, such as dressing treatment, may optionally be carried out tocontrol the exposed state of organic fibers.

The steps of the second production method may be modified to employ thismethod only for the control of fiber content, thereby producing apolishing pad material having no exposed fibers on its surface, and theexposed state of organic fibers may be made by mechanically polishingthe surface. The modified method is the third production method, whereina resin-impregnated sheet-form fiber base material and aresin-unimpregnated sheet-form fiber base material are layered so that aresin-unimpregnated sheet-form fiber base material comprising organicfibers is located on at least one surface. They are then unified bythermocompression molding, to form a polishing pad material having nosurface on which the organic fibers are exposed. The organic fibers areexposed by mechanically polishing the surface of the polishing padmaterial on which the resin-unimpregnated sheet-form fiber material islocated, to obtain the polishing pad of the present invention.

According to the method of polishing a substrate of the presentinvention, a substrate is polished by pressing the substrate against thesurface of the polishing pad of the present invention on which theorganic fibers are exposed, and relatively sliding the substrate and thepolishing pad while an abrasive (CMP abrasive) is being fed between thesubstrate and the polishing pad.

Non-limitative but preferred CMP abrasives usable in the presentinvention are obtainable by dispersing a composition comprising ceriumoxide particles, a dispersing agent and water, and further addingadditives thereto, and contains 0.5 to 20% by weight of cerium oxideparticles. The method of producing the cerium oxide particles is notparticularly limited, and the average particle diameter of the ceriumoxide particles contained in the CMP abrasive is preferably 0.01 to 1.0μm. Cerium oxide particles having an average particle diameter of lessthan 0.01 μm may adversely lower the polishing speed, and those of anaverage particle diameter of more than 1.0 μm tend to make flaws on thefilm being polished.

Examples of usable substrates include a semiconductor substrate on whichcircuit elements and wiring patterns are formed, and a substrate whereina layer of silicon oxide film or silicon nitride film is formed on asemiconductor substrate on which circuit elements are previously formed.By polishing the layer of the silicon oxide film or silicon nitride filmformed on the semiconductor substrate using the CMP abrasive as above,the irregularities on the surface of the layer of the silicon oxide filmis planarized, and a flat surface is formed throughout the semiconductorsubstrate. This method is also applicable to shallow trench isolation.

Any polishing apparatus may be used, such as a disc-type polishingapparatus, a linear-type polishing apparatus or a web-type polishingapparatus. An example is a common disc-type polishing apparatus, whichhas a holder for holding a semiconductor substrate and a fixing disc(equipped with a variable-revolution number motor) for bonding apolishing pad. The polishing condition is not particularly limited, butis preferably adjusted to the optimum one for each matter to bepolished. During polishing, a slurry is continuously fed to the surfaceof the polishing pad by using a pump or the like. The feeding rate ofthe slurry is not limited, but preferably such that the surface of thepolishing pad is always covered with the slurry.

After the polishing, the semiconductor substrate is preferably washed ina stream of water sufficiently, and then dried after the water dropletssticking thereto are blew away by using a spin drier or the like.

The polishing pad of the present invention may be used for polishing notonly a silicon oxide film formed on a semiconductor substrate but alsoan inorganic insulation film formed on a wiring board having desiredwiring, such as a silicon oxide, glass or silicon nitride film,polysilicon, a film consists mainly of Al, Cu, Ti, TiN, W, Ta or TaN,optical glass, such as a photo-mask, a lens or a prism, inorganicconductive film, such as ITO, an optical integrated circuit, an opticalswitching device and an optical guide, which are made of glass and acrystalline material, the end faces of an optical fiber, optical singlecrystal, such as a scintillator, a solid-state laser, a sapphiresubstrate for blue laser LED, semiconductor single crystal, such as SiC,GaP or GaAS, a glass or aluminum substrate for magnetic discs, amagnetic head or the like.

Hereinafter, the present invention will be described referring toExamples, which, however, do not limit the scope of the presentinvention.

EXAMPLES Examples 1 and 2 and Comparative Examples 1 to 3

(Production of Pad)

The following organic fibers were prepared as raw materials.

[Aramid fiber base material “1”]

Para-aramid fiber chops (fiber diameter: 12.5 μm, fiber length: 5 mm,“TECNORA” produced by Teijin, Ltd.) and meta-aramid fiber chops (fiberdiameter: 25 μm, fiber length: 6 mm, softening temperature: 280° C.,non-oriented, “CORNEX” produced by Teijin Ltd.) were mixed and made intoa mat. A 20% by weight aqueous solution of a water-soluble epoxy resinbinder (glass transition temperature: 110° C., trade name: “V-COAT”,produced by Dainippon Ink & Chemicals, Inc.) was sprayed to the mat, anddried by heating (150° C., 3 min.), to give a non-woven fabric of a unitweight of 70 g/m². The weight ratios of para-aramid fiber/meta-aramidfiber/resin binder were 85/5/10. The non-woven fabric was compressedwith heat by passing it through a couple of heating rolls (temperature:300° C., linear pressure: 196 kN/m), to give aramid fiber base material“1”, which was a non-woven fabric wherein the meta-aramid fibers adheredto the para-aramid fibers by thermal fusion. The para-aramid fibers arepoly-p-phenylene-3, 4-diphenyl ether terephthalamide fibers.

The following resin was prepared as a raw material.

[Resin “1”]

Varnish (A) of a bisphenol A epoxy resin (produced by Yuka Shell Co.,Ltd., Trade name: EP-828SK) containing dicyandiamide as a curing agentand 2-ethyl-4-methylimidazole as a curing accelerator was prepared. Forthe preparation of varnish (A), 20 parts by weight of the curing agent,0.1 part by weight of the curing accelerator and 40 parts by weight ofmethyl ethyl ketone as a solvent were used relative to 100 parts byweight of the bisphenol A epoxy resin.

A prepreg sheet for lamination was produced by combining fibers and aresin material.

[Prepreg “1”]

Aramid fiber material “1” was impregnated with varnish (A) and heated todry (170° C., 5 min.), to produce prepreg. The amount of adhering resinwas adjusted so that the thickness became 0.1 mm after thermocompressionmolding. The content of fibers was 50% by weight.

Example 1

A release film (a 50 μm-thick polypropylene film) was put on bothsurfaces of a prepreg layer consisting of 15 sheets of prepreg “1,” putin layers. They were sandwiched between mirror-finished plates andthermocompression molded (temperature: 175° C., pressure: 400 kPa, time:120 min.) between pressing hot plates, with two sheets of 10 mm-thickcushion interposed, to give a 1.5 mm-thick laminate. A polishing pad wasproduced by sticking the laminate to the fixing disc of a polishingmachine, and dressing it with a diamond whetstone of #70 count for 10minutes under a pressure of 8820 Pa (90 g/cm²) at revolutions of 38 rpmto form a very thin layer of exposed aramid fibers on a surface. Theexposed parts of the aramid fibers had a fiber length of 1 mm and afiber diameter of 12.5 μm.

Example 2

A polishing pad was produced by sticking a laminate, which was producedin the same manner as in Example 1, to the fixing disc of a polishingmachine, and dressing it with a diamond whetstone of #150 count for 10minutes under a pressure of 8820 Pa (90 g/cm²) at revolutions of 38 rpmto form a very thin layer of exposed aramid fibers on a surface. Theexposed parts of the aramid fibers were shorter than those of Example 1,and had a fiber length of 500 μm and a fiber diameter of 12.5 μm.

Comparative Example 1

Surface-roughened (35 μm) copper foil was put on both sides of a prepreglayer consisting of 15 sheets of prepreg “1,” put in layers. They weresandwiched between mirror-finished plates, with a release film (a 50μm-thick polypropylene film) interposed between them and themirror-finished plates, and thermocompression molded under the sameconditions as in Example 1 between pressing hot plates, with two10-mm-thick cushions interposed between the mirror-finished plates andthe pressing hot plates, to give a 1.5-mm-thick laminate. The copperfoil on the laminate was etched away with an aqueous ammonium persulfatesolution, to produce a pad that had surfaces having irregularities ofRa=0.9 μm in center line average roughness. The resulting substrate wasstuck to the fixing disc of a polishing machine, but fibers were notexposed on surfaces by any method, such as dressing with a diamondwhetstone. The center line average roughness of Ra=0.9 μm on thesurfaces of the pad was made for holding polishing particles during CMPpolishing.

Comparative Example 2

An existing polishing pad (produced by Rodehl Co., Ltd., IC-1000) madeof a foamed polyurethane resin was stuck to the fixing disc of apolishing machine, and was dressed with a diamond whetstone of #70 countfor 10 minutes under a pressure of 8820 Pa (90 g/cm²) at revolutions of38 rpm.

Comparative Example 3

A pad produced by impregnating a non-woven fabric consisting of bundlesof polyester fibers with a foamed polyurethane resin having lowelasticity was stuck to a fixing disc of a polishing machine, and wasthen used without being subjected any treatment, such as dressing with adiamond whetstone. No fibers were exposed on the surface of the pad.Even after the polishing for evaluation of polishing characteristicsdescribed later, no fibers were exposed on the surface.

The polishing characteristics of the pads produced in Examples andComparative Examples were evaluated as follows.

(Preparation of Cerium Oxide Slurry)

A CMP slurry as an abrasive was prepared as follows.

2 kg of cerium carbonate hydrate was placed in a platinum vessel andcalcined in the air at 800° C. for 2 hours to obtain cerium oxidepowder. 1 kg of the cerium oxide powder was ground by dry grinding byusing a jet mill. 23 g of an aqueous polyammonium acrylate solution (40%by weight) and 8977 g of deionized water were admixed thereto, andultrasonic dispersion was carried out for 10 minutes with stirring. Theresulting slurry was filtered through a 1-μm filter, and deionized waterwas added to obtain 5 wt % slurry. The pH of the slurry was 8.3.Measurement of the slurry particles in the slurry was carried out byusing a laser diffraction granulometer after the slurry was diluted to asuitable concentration for the measurement. D99% of the particlediameter was 0.99 μm.

(Preparation of Insulation Film Substrate Matter to be Polished)

Blanket wafers were prepared by forming 2000-nm silicon oxide film on Sisubstrates of φ127 mm by a TEOS-plasma CVD technique. Test wafers aspolishing subjects were prepared by forming aluminum wiring of a patternof 0.1 mm in width, 1 mm in thickness and 0.1 mm in interval on Sisubstrates of φ 200 mm and forming thereon 2000-nm silicon oxide film bya TEOS-plasma CVD technique.

(Polishing Method and Evaluation of Polishing) Characteristics

Each of the former wafer was set to a holder bearing an absorbent padstuck thereto for attaching a wafer substrate was stuck, and the holderwith the insulation film looking downward was placed on a fixing disc ofφ380 mm to which a polishing pad produced as above had been stuck, andthe processing load was set to 300 gf/cm² (3.04×10⁴Pa). The insulationfilm was polished by rotating the fixing disc and the wafer at 38 rpmfor 2 minutes while the above-described cerium oxide abrasive (solidscontent: 1% by weight) was dropped on the fixing disc at a rate of 150cc/min. The polished wafer was washed with pure water sufficiently, andthen dried. The difference between the film thicknesses before and afterthe polishing was determined by using a light interference filmthickness measuring apparatus, and the polishing speed was calculated.As to the evaluation of polishing flaws, the surface of the polishedwafer was observed by using a dark-field microscope, to count the flawsmade on the surface of the wafer due to polishing.

As to the evaluation of flatness, 1 μm of the difference in levelbetween the convexes and the concaves of each TEG wafer was ground, andthe final difference in level was measured before the aluminum at theconvexes was exposed.

The results of these evaluations on the polishing pads produced inExamples and Comparative Examples are listed in Table 1. The resultsshow that as compared with the polishing pads of Comparative Examples(prior art), those of Examples according to the present invention hadhigher polishing speed and made less polishing flaws while ensuringflatness. The results of Examples 1 and 2 show that longer fibersexposed on a surface make less polishing flaws, and shorter fibers makebetter flatness. This indicates that desired polishing characteristicscould be attained by controlling fiber length.

TABLE 1 Polishing pad Material/ Diamond State of Sample Structuredressing surface Ex. 1 aramid fiber/  70 count/10 min Fibers wereexposed epoxy resin on resin. 2 aramid fiber/ 150 count/10 min Fiberswere exposed epoxy resin on resin. Comp. 1 aramid fiber/ No fineirregularities Ex. epoxy resin on surface 2 foamed  70 count/10 minfoaming pores polyurethane (φ30 μm) resin 3 polyester fiber/ Nocontinuous foamed foaming polyurethane pores resin Polishingcharacteristics Polishing speed Number of Polishing Flatness Sample(nm/min) Flaws (number/wafer) (nm) Ex. 1 240 0 50 2 270 10 30 Comp. 1250 210 20 Ex. 2 180 30 30 3 120 0 250

Examples 3 to 7

(Production of Pad)

The following organic fibers were prepared as raw materials.

[Polyester Fiber Base Material “1”]

A non-woven fabric consisting of polyester fibers having a fiberdiameter of 12.5 μm and a fiber length of 5 mm and having a unit weightof 70 g/m² ([EPM-4070TE] produced by Nippon Byleen Co., Ltd.).

[Aramid fiber base material “2”]

Para-aramid fiber chops (fiber diameter: 12.5 μm, fiber length: 5 mm,“KEVLAR” produced by DuPont Kabushiki Kaisha), para-aramid fiber pulps(fiber diameter: 0.83 μm, fiber length: 1 mm, “KEVLAR” produced byDuPont Kabushiki Kaisha) and meta-aramid fiber chops (fiber diameter: 25μm, fiber length: 6 mm, softening temperature: 280° C., “CORNEX”produced by Teijin Ltd.) were mixed and made into a mat. A 20% by weightaqueous solution of a water-soluble epoxy resin binder (glass transitiontemperature: 110° C., trade name: “V-COAT”, produced by Dainippon Ink &Chemicals, Inc.) was sprayed to the mat, and dried by heating (150° C.,3 min.). The mat was then compressed with heat by passing it through acouple of heating rolls (temperature: 300° C., linear pressure: 196kN/m), to give aramid fiber base material “2”, which was a non-wovenfabric wherein meta-aramid fiber chops adhered to para-aramid fiberchops by thermal fusion. The aramid fiber base material “2” had a unitweight of 70 g/m², and the weight ratios of para-aramid fiberchop/para-aramid fiber pulp/meta-aramid fiber chop/epoxy resin binderwere 58/17/8/17. The para-aramid fibers are poly-p-phenyleneterephthalamide fibers.

Prepreg sheets for lamination were produced by combining the fibers anda resin material.

[Prepreg “2”]

Polyester fiber base material “1” was impregnated with varnish (A) andheated to dry (170° C., 5 min.), to produce prepreg. The amount ofadhering resin was adjusted so that the thickness became 0.1 mm afterthermocompression molding. The content of polyester fibers afterthermocompression molding was 50% by weight.

[Prepreg “3,”]

Aramid fiber base material “2” was impregnated with varnish (A) andheated to dry under the same conditions as for prepreg “2”, to produceprepreg. The amount of adhering resin was adjusted so that the thicknessbecame 0.1 mm after thermocompression molding. The content of aramidfibers after thermocompression molding was 50% by weight.

[Prepreg “4”]

A glass fiber woven fabric (unit weight: 107 g/m², “GC-216” produced byAsahi Schueber) was impregnated with varnish (A) and heated to dry underthe same conditions as for prepreg “2”, to produce prepreg. The amountof adhering resin was adjusted so that the thickness became 0.1 mm afterthermocompression molding. The content of glass fibers afterthermocompression molding was 60% by weight.

Example 3

10 sheets of prepreg “2” and 10 sheets of polyester fiber base material“1” impregnated with no resin were layered so that prepreg “2” andpolyester fiber base material “1 ” were layered alternately, andthermocompression molded in the same manner as in Example 1, to obtain a1.5-mm-thick laminate. The fiber content in the whole laminate was 67%by weight. One surface of the laminate (the surface made of polyesterfiber base material “1” impregnated with no resin) was dressed in thesame manner as in Example 2 to form a very thin layer of exposedpolyester fibers (the exposed polyester fibers had a fiber length of 500μm and a fiber diameter of 12.5 μm), thereby obtaining a polishing pad.

Example 4

10 sheets of prepreg “3” and 10 sheets of aramid fiber base material “2”impregnated with no resin were layered so that prepreg “3” and aramidfiber base material “2” were layered alternately, and thermocompressionmolded in the same manner as in Example 1, to obtain a 1.5-mm-thicklaminate. The fiber content in the whole laminate was 67% by weight. Onesurface of the laminate (the surface made of fiber base material “2”impregnated with no resin) was dressed in the same manner as in Example2 to form a very thin layer of exposed aramid fibers (the exposed aramidfibers had a fiber length of 500 μm and a fiber diameter of 12.5 μm),thereby obtaining a polishing pad.

Example 5

A polishing pad was produced in the same manner as in Example 4 exceptthe surface of the laminate was not dressed. Even in this case, a verythin layer of exposed aramid fibers (the exposed aramid fibers had afiber length of 2 mm and a fiber diameter of 12.5 μm), though not somuch as in Example 4, was formed on the surface made of aramid fiberbase material “2” impregnated with no resin.

Example 6

14 sheets of prepreg “3” were layered, and 2 sheets of aramid fiber basematerial “2” impregnated with no resin were layered thereon, and theywere thermocompression molded in the same manner as in Example 1, toobtain a 1.5-mm-thick laminate. The fiber content in the surface layerof the laminate (a layer comprising aramid fiber base material “2”impregnated with no resin and the resin that oozed out from theunderlying layer on the thermocompression molding and was partially keptin the aramid fiber base material “2” impregnated with no resin) was 67%by weight. One surface of the laminate (the surface made of fiber basematerial “2” impregnated with no resin) was dressed in the same manneras in Example 2 to form a very thin layer of exposed aramid fibers (theexposed aramid fibers had a fiber length of 500 μm and a fiber diameterof 12.5 μm), thereby obtaining a polishing pad.

Example 7

14 sheets of prepreg “4” were layered, and 2 sheets of aramid fiber basematerial “2” impregnated with no resin were layered thereon, and theywere thermocompression molded in the same manner as in Example 1, toobtain a 1.5-mm-thick laminate. The fiber content in the surface layerof the laminate was 67% by weight. One surface of the laminate (thesurface made of fiber base material “2” impregnated with no resin) wasdressed in the same manner as in Example 2 to form a very thin layer ofexposed aramid fibers (the exposed aramid fibers had a fiber length of500 μm and a fiber diameter of 12.5 μm), thereby obtaining a polishingpad.

Comparative Example 4

15 sheets of prepreg “3” were layered and thermocompression molded inthe same manner as in Example 1, to obtain a polishing pad that was a1.5-mm-thick laminate subjected to no dressing treatment on its surface.The fiber content in the whole laminate was 50% by weight. On thesurface of the polishing pad, only epoxy resin was observed, and nofiber was exposed. Even after the polishing for the evaluation ofpolishing characteristics described later, no fiber was exposed.

The polishing characteristics of the polishing pads produced in Examples3 to 7 and Comparative Example 4 were evaluated in the same manner asthat described above, and the ressults are listed in Table 2.

TABLE 2 Polishing pad Material/ Diamond State of Sample Structuredressing surface Ex. 3 polyester fiber/ 150 count/10 min Fibers wereexposed epoxy resin on resin. 4 aramid fiber/ 150 count/10 min Fiberswere exposed epoxy resin on resin. 5 aramid fiber/ No Fibers wereexposed epoxy resin on resin. 6 aramid fiber/ 150 count/10 min Fiberswere exposed epoxy resin on resin. 7 aramid fiber/ 150 count/10 minFibers were exposed glass fiber/ on resin. epoxy resin Comp. 4 aramidfiber/ No no exposed fibers Ex. epoxy resin (epoxy resin only) Polishingcharacteristics Polishing speed Number of Polishing Flatness Sample(nm/min) Flaws (number/wafer) (nm) Ex. 3 240 0 30 4 270 0 30 5 200 90 206 270 0 30 7 270 0 30 Comp. 4 10 250 could not be Ex. determined

Examples 8 to 12

(Production of Polishing Pad)

The following organic fibers were prepared.

[Arimid Fiber Base Material “3”]

Arimid fiber base material “3” that is a non-woven fabric was producedin the same manner as in the production of aramid fiber base material“1” except the para-aramid fibers were changed from the poly-p-phenylene3,4-diphenyl ether terephthalamide fiber chops to poly-p-phenyleneterephthalamide fiber chops (fiber diameter: 1.5 deniers (12.5 μm),fiber length: 5 mm, “KEVLAR” produced by Du Pont Kabushiki Kaisha).

[Aramid Fiber Base Material “4”]

Aramid fiber base material “4” that is a non-woven fabric” was producedin the same manner as in the production of aramid fiber base material“1” except the para-aramid fiber chops were not used but onlymeta-aramid fiber chops (fiber diameter: 3 deniers (25 μm), fiberlength: 6 mm, softening temperature: 280° C., “CORNEX” produced byTeijin Ltd.) were used.

[Polyester Fiber Base Material “2”]

A woven fabric having a weave density of 48 fibers in length/48 fibersin width, a unit weight of 130 g/m², a fiber diameter of 3.0 deniers (25μm) (“BKE POPRIN” produced by Asahi Chemical Industry Co., Ltd.).

The following prepregs were prepared.

[Prepreg “5”]

Aramid fiber base material “3” was impregnated with varnish (A) andheated to dry (170° C., 5 min., the same will be applied hereinafter),to produce prepreg. The amount of adhering resin was adjusted so thatthe thickness became 0.1 mm after thermocompression molding. The contentof aramid fibers after thermocompression molding was 50% by weight.

[Prepreg “6”]

Aramid fiber base material “4” was impregnated with varnish (A) andheated to dry, to produce prepreg. The amount of adhering resin wasadjusted so that the thickness became 0.1 mm after thermocompressionmolding. The content of aramid fibers after thermocompression moldingwas 50% by weight.

[Prepreg “7”]

Polyester fiber base material “2” was impregnated with varnish (A) andheated to dry, to produce prepreg. The amount of adhering resin wasadjusted so that the thickness became 0.1 mm after thermocompressionmolding. The content of aramid fibers after thermocompression moldingwas 50% by weight.

Example 8

A 1.5-mm-thick laminate was produced by thermocompression molding 15sheets of prepreg “3” in the same manner as in Example 1.

Example 9

A 1.5-mm-thick laminate was produced by thermocompression molding 15sheets of prepreg “5” in the same manner as in Example 1.

Example 10

A 1.5-mm-thick laminate was produced by thermocompression molding 15sheets of prepreg “6” in the same manner as in Example 1.

Example 11

7 sheets of prepreg “1” were layered for a surface layer, and, beneaththem, 8 sheets of prepreg “7” were layered for backing layer. They arethen thermocompression molded in the same manner as in Example 1, toobtain a 1.5-mm-thick laminate.

Example 12

7 sheets of prepreg “3” were layered for a surface layer, and, beneaththem, 8 sheets of prepreg “7” were layered for backing layer. They arethen thermocompression molded in the same manner as in Example 1, toobtain a 1.5-mm-thick laminate.

Comparative Example 5

A 1.5-mm-thick laminate was produced by thermocompression molding 15sheets of prepreg “4” in the same manner as in Example 1.

The laminates obtained in Examples 8 to 12 and Comparative Example 5were used as polishing pad materials, which were dressed in the samemanner as in Example 2, to obtain polishing pads. The polishingcharacteristics of the polishing pads are listed in Table 3. Among thepolishing characteristics, the number of polishing flaws, polishingspeed and flatness were evaluated in the same manner as that describedabove. Polishing evenness was evaluated by measuring the polishingspeeds of a silicon oxide film at various points on the surface of asilicon wafer, and obtaining the average polishing speed and standarddeviation thereof, and was presented by the percentage of the latterbased on the former. The durability of the polishing pads were presentedin Table 3 by indexes when the life-time of the polishing pad ofComparative Example 2 (IC-1000, produced by Rodehl Co., Ltd.), which isa prior art polishing pad made of a foamed polyurethane resin, isdefined as 100.

TABLE 3 Polishing Pad Surface layer Backing layer Material MaterialState of Surface Ex. 8  aramid fibers (size no backing layer Fibers wereexposed combination)/ on resin. epoxy resin Ex. 9  para-aramid fiber/ nobacking layer Fibers were exposed epoxy resin on resin. Ex. 10meta-aramid fiber/ no backing layer Fibers were exposed epoxy resin onresin. Ex. 11 aramid fiber/ polyester fiber/ Fibers were exposed epoxyresin epoxy resin on resin. Ex. 12 aramid fibers (size polyester fiber/Fibers were exposed combination)/ epoxy resin on resin. epoxy resinComp. glass fiber/ no backing layer surface having fine Ex. 5 epoxyresin irregularities/ little exposure of fibers Polishing flawsPolishing Evenness of (number/ speed Flatness polishing wafer) (nm/min)(nm) (%) Durability Ex. 8  5 250 20 8 95 Ex. 9  10 250 40 8 95 Ex. 10 2200 100 8 75 Ex. 11 10 250 40 4 100 Ex. 12 5 250 30 4 95 Comp. ≧1000 15050 4 120 Ex. 5

Comparison of Example 8 and Example 2 indicates that combiningrelatively thicker fibers with thinner fibers effectively improves theflatness of the polished surface of a substrate. Comparison of Example 9and Example 10 indicates the durability of a polishing pad is improvedby using para-aramid fibers in place of meta-aramid fibers. From theresults of Example 11 and Example 12, it was confirmed that evenness ofpolishing could be improved by providing beneath a surface layer abacking layer containing fibers having a lower elastic modulus than thatof fibers contained in the surface layer.

INDUSTRIAL APPLICABILITY

According to the polishing method of a substrate of the presentinvention using the polishing pad for CMP of the present invention thatis produced by exposing organic fibers on the surface of an elastic bodymade of a resin, a step of planarizing interlayer insulation film, aBPSG film (a silicon dioxide film doped with boron and phosphorus) and astep of constituting shallow trench isolation can be carried outefficiently, while suppressing the occurrence of flaws on the substrate.

According to the production method of the present invention, thepolishing pad having organic fibers exposed on its surface can beproduced easily, and the content of organic fibers in the polishing padcan be varied easily depending on the purposes for which the polishingpad is used.

1. A polishing pad for polishing a substrate or a thin film formed on a substrate, which polishing pad comprises a substantially non-porous surface layer and contains organic fibers exposed on a surface of the polishing pad, wherein the surface on which the organic fibers are exposed is a surface of the surface layer, and wherein the organic fibers are para-aramid fibers or consist chiefly of para-aramid fibers; and wherein the organic fibers are exposed on a surface of the surface layer in a length of 10 μm to 1 cm.
 2. The polishing pad of claim 1, wherein the para-aramid fibers are poly-p-phenylene diphenyl ether terephthalamide fibers.
 3. The polishing pad of claim 1, wherein the organic fibers exposed on the surface layer of the polishing pad have a diameter of 1 mm or less.
 4. A method of polishing a substrate, comprising pressing the substrate against the surface of the polishing pad of any one of claims 1, 2 and 3, on which the organic fibers are exposed, and relatively sliding the substrate and the polishing pad while an abrasive is being fed between the substrate and the polishing pad.
 5. A polishing pad for polishing a substrate or a thin film formed on a substrate, which polishing pad comprises a substantially non-porous surface layer and contains organic fibers exposed on a surface of the polishing pad, wherein the surface on which the organic fibers are exposed is a surface of the surface layer, and wherein the organic fibers are meta-aramid fibers or consist chiefly of meta-aramid fibers; and wherein the organic fibers are exposed on a surface of the surface layer in a length of 10 μm to 1 cm.
 6. The polishing pad of claim 5, wherein the organic fibers exposed on the surface layer of the polishing pad have a diameter of 1 mm or less.
 7. A method of polishing a substrate, comprising pressing the substrate against the surface of the polishing pad of any one of claims 5 and 6 on which the organic fibers are exposed, and relatively sliding the substrate and the polishing pad while an abrasive is being fed between the substrate and the polishing pad.
 8. The polishing pad of one of claims 1 and 5, wherein the polishing pad is made of a substantially non-porous polishing pad material comprising a resin and the organic fibers contained in the resin by mechanically polishing a surface of the polishing pad material to form the surface of the polishing pad on which the organic fibers are exposed.
 9. The polishing pad of claim 8, wherein the surface of the polishing pad on which the organic fibers are exposed is produced by mechanically polishing the polishing pad material by using a dresser attached to a polishing apparatus.
 10. The polishing pad of one of claims 1 and 5, wherein the polishing pad is produced by thermocompression molding of a molding material containing the organic fibers and a resin, and wherein the surface of the polishing pad on which the organic fibers are exposed is produced at the time of the thermocompression molding by layering a resin-impregnated sheet-form fiber base material and a resin-unimpregnated sheet-form fiber base material so that a resin-unimpregnated sheet-form fiber base material comprising organic fibers is located on at least one surface, and unifying them by thermocompression molding.
 11. A polishing pad having a multilayer structure, comprising the polishing pad of any one of claims 1, 2, 3, 5 and 6, and a backing layer having an elastic modulus lower than the surface layer of the polishing pad, which are laminated together.
 12. A method of polishing a substrate, comprising pressing the substrate against the surface of the polishing pad of claim 8 on which the organic fibers are exposed, and relatively sliding the substrate and the polishing pad while an abrasive is being fed between the substrate and the polishing pad.
 13. A method of polishing a substrate, comprising pressing the substrate against the surface of the polishing pad of claim 9 on which the organic fibers are exposed, and relatively sliding the substrate and the polishing pad while an abrasive is being fed between the substrate and the polishing pad.
 14. A method of polishing a substrate, comprising pressing the substrate against the surface of the polishing pad of claim 10 on which the organic fibers are exposed, and relatively sliding the substrate and the polishing pad while an abrasive is being fed between the substrate and the polishing pad.
 15. A method of polishing a substrate, comprising pressing the substrate against the surface of the polishing pad of claim 11 on which the organic fibers are exposed, and relatively sliding the substrate and the polishing pad while an abrasive is being fed between the substrate and the polishing pad. 